The present invention broadly relates to the machine tool art and, more particularly, to an improved tool holder system and method of utilizing the same.
As is well known, various tool holders have been utilized in the prior art which interface with a rotating spindle of a machine tool such as a milling or boring machine to securely hold a cutting tool upon the machine during cutting of a workpiece. For the past fifty to sixty years it was customary practice for such tool holders to be manually inserted into the spindle of the machine tool and subsequently be drawn or pulled tightly into the spindle by way of a threaded draw bar extending axially through the spindle and into the end of the tool holder. However, with the relatively recent advent of high production numerical control and computer control machine tools, automated tool holder changers have been introduced which mechanically insert and remove the tool holder from the spindle of the machine tool.
In order to enable standardization in the manufacture of automated tool changer systems, basically four tool holder dimensional and configurational standards have been introduced in the machine tool art. These standards basically comprise: (1) the American standard, (2) the European DN standard, (3) the Japanese BT standard, and (4) the Caterpillar V-flange standard. These various tool holder dimensional and configurational standards are well known in the art and although all include various similarities in design, they each possess peculiar design features which have heretofore prevented their interchangability in various automated tool holder changer systems. In this regard, a particular automated tool holder changer system could only be utilized or interfaced with a particular one of the standard tool holder configurations. Thus, in most instances, inventory of all of the above-standard tool holders has been required which, as will be recognized, adds substantially to overall production costs and reduces production efficiency. Further, such standard tool holder configurations utilized for automated tool holder changers have typically not been adaptable to be utilized in manual systems thereby additionally increasing overall inventory costs.
In addition to the above-mentioned inventory deficiencies, modern high tolerance machining techniques have further dictated that current tool holders be capable of permitting rapid height adjustment setting of the cutting tool within the tool holder and subsequently prevent any movement, i.e. backing out of the cutting tool from the tool holder during machining of a workpiece. It has been customary practice that this positioning or presetting of the height of the cutting tool within the tool holder be accomplished in a manual trial and error method with the machinist manually reciprocating the shank portion of the cutting tool within the central aperture of the tool holder. Once the height was manually obtained and verified, securing of the cutting tool within the tool holder was typically accomplished by way of a set screw extending perpendicularly through the tool holder to tightly contact or abut a flat formed on the shank portion of the cutting tool. As will be recognized, this manual trial and error method of setting the cutting tool height within the tool holder has proven timely and costly while the retention of the cutting tool within the tool holder by use of the perpendicularly disposed set screw has often resulted in the backing out of the cutting tool from the tool holder during the machining operation. Although recently this backing out deficiency has been recognized wherein a set screw has been inclined from the perpendicular to prevent the cutting tool from backing out of the tool holder, the height setting deficiencies have not to date been addressed in the prior art.
Further, due to the central aperture of the tool holders typically being formed approximately one to two ten-thousandths of an inch greater in diameter than the shank portion of the cutting tool to enable manual reciprocation of the cutting tool within the tool holder, all of the prior art tool holders have been susceptible to non-concentric mounting of the cutting tool therein which in modern high tolerance machining applications has proved unacceptable.
Thus, there exists a substantial need in the art for an improved tool holder system and method of use which reduces the inventory requirements of the various standard tool holder configurations, permits use of the tool holder in both manual and automatic tool changer systems, permits ease in setting tool height within the tool holder, prevents backing out of the cutting tool from the tool holder during the machining operation, and ensures concentric mounting of the cutting tool within the tool holder.